1. Field of the Invention
The present invention relates to a transporting apparatus, and more particularly, to a transporting apparatus which can horizontally transport a carrier with an air bearing of which a rotational degree of freedom is kept relative to a surface of a base.
2. Description of the Related Art
Generally, transporting machines used in various industry fields have been steadily developed with a high capacity, a small and lightweight structure (fine structure), and a high speed to achieve desired objects such as mass production, performance improvement, etc. Particularly, in a case of an apparatus for inspecting a semiconductor wafer, a liquid crystal display (LCD), etc., this apparatus is required to be excellent in cleanness, durability and accuracy, and accordingly requirements for introduction of an air bearing used with this apparatus are increasing.
The air bearing generates no friction due to a contact with a surface of a base, so that the air bearing can smoothly operate at a high speed with no noise. Further, the air bearing has a higher accuracy than other kinds of bearings and produces relatively less contaminant because the air bearing does not use oil as a lubricant. Such an air bearing is widely classified into a mass preload type, a magnet preload type and a vacuum preload type. Particularly, the vacuum preload type air bearing is being widely used because it is excellent not only in transport for a flat surface but also in accuracy.
As shown in FIG. 1, a conventional transporting apparatus for a precise component has a structure in which an air bearing 1 and a carrier 2 are firmly connected with each other through a connector 3. The connector 3 has a lower part shaped like a ball and movably coupled to the air bearing 1 by a retainer 4, and an upper part coupled to the carrier 2 by a fastening nut 5.
The air bearing 1 generates a thin layer of air using a pneumatic structure so that the carrier 2 and the air bearing 1 float on the thin layer of air at a predetermined distance from a surface of a base 6. At this time, if the base 6 has an irregular surface, the connector 3 has to keep a rotational degree of freedom of the air bearing 1 and a horizontal state of the carrier 2 on which the precise component are placed, thereby maintaining accuracy and reliability of the transporting apparatus. Further, the fastening nut 5 allows a height of the carrier 2 to be adjusted.
In a case that the conventional transporting apparatus employs the mass preload type or magnet preload type air bearing 1, a constant load weight vertically presses the connector 3, so that a minute gap between the connector 3 and the air bearing 1 is removed. Therefore, a space is not left between the connector 3 and the air bearing 1 even if the air bearing 1 goes through the irregular surface of the base 6, thereby keeping the horizontal state of the carrier 2.
In the meantime, in a case that the conventional transporting apparatus employs the vacuum preload type air bearing 1, contrary to the mass preload type or magnet preload type air bearing 1, a distance between the air bearing 1 and the surface of the base 6 is kept constant by discharging and inhaling air. Therefore, if the air bearing 1 goes through the irregular surface of the base 6, the space is left between the connector 3 and the air bearing 1 because of the minute gap between the connector 3 and the air bearing 1. Such space causes the carrier 2 to sway and incline, thereby decreasing the accuracy and the reliability of the transporting apparatus.
Further, in the conventional transporting apparatus, the connector 3 causes the carrier 2 to be positioned relatively higher than the surface of the base 6, thereby causing the accuracy and the reliability of the transporting apparatus to be decreased.